"No matter the season, no matter the weather condition, the gorge is always beautiful" Moon Handbooks.

When I come across this kind of matter-of-fact type of statement I usually take them with a good degree of skepticism. Moon Handbooks are among the best travel guides, but does the Gorge really deserve this reputation? Well, after visiting the Columbia River Gorge, I can certainly say it definitely does.
What is normally referred to as CRG is really only the final stretch of the Columbia River. This majestic river stretches from Canada to reach Washington State, forming much of the border between Washington and Oregon.
The scenic byway I'm writing about is actually made of three roads.
The most famous is the Columbia River Gorge Historical Hwy, which covers less than 20 miles on the southern (Oregon) side of the Gorge. In this short stretch you'll find all the famous waterfalls as well as the best viewpoints. The southern side is completed by I-84 that stretches from Portland to the town of The Dalles.
Once you get there, cross the river and you will be in the State of Washington where you can take Hwy-14 back to Portland or, if you're headed towards the Cascades, turn north abound half way from Portland and head towards the eastern side of Mt St Helens, Mt Adams and Mt Rainier.
The entire trip (from Portland to The Dalles and back) is approximately 140 miles and can easily take a whole day. There are plenty of motels along the way, including many of the most famous national chains motels (Motel6, Super8, Bestwestern ...) in The Dalles and around Portland. I have been at the Super8 of The Dalles, where I found the usual Super8 amenities for a relatively good price. Only one negative note, while breakfast was complimentary, it was really a pretty modest one.
Spring and Fall are certainly the best seasons to visit the Gorge whereas in summer you'll find many of the waterfalls pretty dry. But do not despair, a couple of rainy days are enough to get those waterfalls' flow strong again.

The southern side (Oregon)

Our trip starts from Troutdale OR, a few miles east of Portland. Within minutes you'll get to the true Historical Columbia River Gorge Hwy.
The first stop I recommend is at the Women's Forum Overlook. If the name puzzles you, the overlook will leave you speechless in front of what is one of the best panoramic views of the Gorge. The view extends pretty much endlessly eastward showing the Gorge that, slow but inexorable, curve after curve defines and molds the landscape around it. Not far away you can see the Vista House, and that is what should be your next stop.
Here I'd like to recommend a relatively short detour to Sherrard Point. Take the Larch Mountain turnout, it's a 14 miles long one way road taking you through a green forest at the end of which you will find a parking lot. Leave the car here (you'll need a Northwest Forest Pass to park) and take the short trail starting at the parking lot. Once on top of a small hill you'll enjoy one of the finest views of this area, with Mt Hood, Mt St. Helens, Mt Rainier, Mt Adams and Mt Jefferson around you.
Once you get back on the Columbia River Gorge Historical Hwy, stop at Crown Point Overlook where the Vista House I previously mentioned is located. If you googled the Columbia River Gorge you must have seen at least one picture of the Vista House. Its small dome is unique and offers excellent opportunities for photos with the beautiful Gorge in the background.
We are now entering one of the most incredible stretches of the Gorge, where one after the other you will see dozens of beautiful waterfalls.
First stop is at Latourell Falls. A short trail leads to a first viewpoint, but you can continue a bit and get much closer to the waterfall. A little over a mile away, stop again to check Shepperd's Dell Fall out.
Next stop worth your time is at Bridal Veil Falls. Here a short trail (less than a mile round trip) takes you to the waterfalls. Technically you are in the Bridal Veil State Park and aside from the waterfalls, there is also a short loop that leads to three similar overlooks on Gorge.
Continuing east you should not miss Wahkeena Falls. Here you can see the falls pretty much from the edge of the road but I suggest you hike the short trail and get a bit closer to the falls. Near the parking lot there are plenty of picnic tables, just in case you want to relax a bit a grab a bite. Bring a juicy Porterhouse and challenge the other Americans who are cooking huge steaks on one of several barbecue grills available.
The next stop is at Multnomah Falls, certainly the most famous waterfalls of the Gorge. You can park in the parking lot or, alternatively, reach the falls by following a trail that starts from Wahkeena Falls. The Multnomah Falls are incredibly high and you should at least try to reach the famous bridge mid way from the upper viewpoint. To comprehend the size of the waterfalls look at the base of the lower falls and you'll see a boulder. It does not seem very big when compared to the waterfalls but a interpretive sign will tells you that the boulder is the size of a school bus.

A visitor center is located just in front of Multnomah Falls. In addition to all sort of information, maps and brochures, check the waterfalls photo archive. This will help you choose what you want to see.
There is so much to see that one day is certainly not enough to explore everything the Gorge has to offers. My advice is to choose at least one waterfall that involves a decent hike so that you won't spend the whole day driving and can enjoy the lush green of the forests of this area.
The next stop I'd suggest is at the Horsetail Falls. These graceful and very tall falls are among my favorites. They are literally on the edge of the road but worth a stop to thoroughly enjoy the view.
You're now at the end of the Columbia River Gorge Historical Hwy and will need to continue on I-84, another area full of opportunities for short hikes. I haven't personally been there but I heard very good things about the Punch Bowl Falls along Eagle Creek Trail.
Instead I choose Wahclella Falls. The trail that leads to the waterfall is about a mile one way and leads through a beautiful forest with huge rock walls on either side of the stream. The waterfalls are truly spectacular, worthy of the effort required to get there. They also offer many photographic opportunities and you can shoot from a dozen different angles. Remember that a Northwest Forest Pass is required to park at the trailhead parking lot.
The area known for its waterfalls is over but there are many other great stops ahead of you. An interesting one is at Cascade Locks, with their famous canals.
After leaving the town I-84 continues along the Gorge and it's only a matter of choosing whether you want to make more stops or simply enjoy the stunning views driving along the highway.
If you plan an overnight stop The Dalles is a good choice. The town is small but with plenty of motels, fast food and restaurants. At this point you also need to choose whether you want to further explore the southern side of the Gorge and continue driving east or cross the river and come back driving on the northern side.

The northern side (Washington)

The northern part of the Gorge is not as rich as the southern yet there is still abundance of great views. The rocks the road winds through reminded me of the type of rock around Lake Powell, both for their color and shape.
A couple of stops that are definitely worth are Maryhill Museum of Art in Goldendale and the Columbia River Gorge Interpretative Center where, among other things, you'll find the largest collection of rosaries in the world.
Well, the trip ends in Portland, you can leave the Gorge to head north visiting the eastern side of Mt St. Helens, Mt Adams, and finally, enter Mt Rainier NP through its south-eastern entrance.